Abstract
A resonant-ring-assisted large mode area segmented cladding fiber (RR-SCF) with a high-index ring in the core is proposed. Numerical investigations of the effects of the high-index ring on the leakage losses of guiding modes, mode area, and electric field distribution of FM of the proposed fiber show the high-index ring not only increases the ratio of the loss between the fundamental mode (FM) and the higher-order modes (HOMs) but also improves the electric field distribution of the FM to be flat. By taking these advantages of the high-index-ring-assisted core, the effective single-mode (SM) operation is achieved in the proposed fiber bent in any orientation, which makes up the defect of the conventional RR-SCF that the SM output is affected by the bending orientation. Meanwhile, the mode area is enlarged. Furthermore, the effects of the heat load, duty cycle, bending, and operation wavelength on the fiber performance are analyzed. The results show single-mode operation in all bending orientations with a mode area larger than 824 μm2 can be achieved at a tight bending radius of 15 cm to 16 cm when the operating wavelength ranges from 1.06 μm to 1.76 μm. This fiber shows great potential in high-power fiber lasers.
Highlights
Over the last few years, high-power fiber lasers have developed fast due to their advantages such as compact system designs, high output efficiency, good power handling, and better thermal management [1]–[5]
In order to overcome the difficulty caused by the optical nonlinear effect, several special large mode area (LMA) fibers operating with effective single-mode (SM) are proposed [14]–[15]
The leakage loss of LP01 mode (FM) of the ring-assisted large mode area segmented cladding fiber (RR-segmented cladding fibers (SCFs)) is kept lower than 0.1 dB/m when the bending orientation varies, the lowest loss of the higher-order modes (HOMs) isn’t higher than 1 dB/m when the bending orientation angle ≤4.5°, which can’t meet the requirement for effective single-mode operation. This sensitivity to bending orientation means when it is applied as a gain medium in a fiber laser system, the coiled RR-SCF has to be properly fixed to avoid the degradation of HOMs suppression
Summary
Over the last few years, high-power fiber lasers have developed fast due to their advantages such as compact system designs, high output efficiency, good power handling, and better thermal management [1]–[5]. Novel designs include photonic crystal fibers (PCFs) [16], leakage channel fibers (LCFs) [17]– [18], brag fibers (BFs) [19], all-solid photonic bandgap fibers (AS-PBFs) [20], chirally-coupled-core fibers (CCCFs) [21], Gain-guided, index anti-guided fibers (GG+IAGFs) [22], segmented cladding fibers (SCFs) [23], single-trench fibers (STFs) [24], and multi-trench fibers (MTFs) [25]–[26] Among these elaborate designs with different performances of SM operation and mode areas, SCFs show an attractive prospect due to their all-solid structures and potential to achieve SM operation and large mode area over a wide range of operating wavelengths. The performance of single-mode operation with a large mode area over a range of wavelengths makes the fiber a good candidate for fiber lasers
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